Electromagnet structure



f June 13, 1944.

fl'l' 2 A. WARSHER ELECTRO-MAGNET STRUCTURE Filed Sept. 25, 1940 2Sheets-Sheet l IIIIIIIII INVENTOR dol/Ufa fa/Sez #MVM M ATTO R N EYSJune 13, 1944. ,1 WARSHER 2,351,377

ELECTRO-MAGNET STRUCTURE Filed sept. 25, 1940 2 sheets-sheet 2 INVENTORAT ORNEY5 Patented June 13, 1944 STRUCTURE Adolph Wsrsller, Haywood. N.I., to Harwell geene alignments,

assigner n. anni Application september 2s, 1m. 'serial No. 35am sclean.. (ci. zoew The present invention, while vshown applied to anelectromagnetic relay of special utility in the starting and operationof thermionic lamps is of more general application to otherconstructions of electromagnets and relays 'for other purposes.

The invention constitutes an improvement upon that described and claimedin the prior Patent No. 2,159,837 granted to Duro Test Corporation onMay 23, 1939, on application illed by Maynard A. Babb and Samuel-J. A.M. Bagno.

Among the objects of the invention are to provide a relay comprisingreadily vstamped parts, easily assembled with a high'degree of accuracyfrom a number of sub-assemblies each of which in turn is readily andaccurately assembled.

. Another object is to provide a magnetic yoke structure the relativesliding displacement or lateral separation of the laminations of whichis precluded in the course of impregnation, ad-

of theyoke. showing the mode of assemblingthssame,

Hg. 5 is a and contact lub-assembly,

Fig. 6 is an exploded perspective view oi' the armature and contactsub-assembly.

02g. 'l is a perspective view of the auxiliary y i Iig. 8 is atransverse l-t of-Fig. 7, and' una larger scale,

Fig. 9 is a perspective view on a largerscale of the armature holderbracket, and

Ilig.- l0 is a transverse sectional detail view- 4 takenfon line t-l ofFig.

justment and use, and assembly of which with Athe electromagnetic coilis easily effected, witho'ut the likelihood of tearing or scuillng thepaper liner-thereof or short' circuiting or otherwise disturbing thepredetermined fixed small air gap of the yoke structure.

Another object is to provide an electromagnet structure of the foregoingtype, in which without the need for annealing and heat treating themagnetic parts `to that end, release of the armature is promptlyeifected without delay due to magnetic retentivity upon collapse of themagnetic field, and this without imposing an undue mechanical load uponthe coil in effecting attraction of the armature.

Another object is to provide a relay of th above type in which theeifectiveness of contact operation is not impaired by any stressesevolved in the course of use as for example those due to heat, thatmight cause among other disturbances the warping of heat insulatingcarrying parts. and in which contact is resiliently maintained closedwith a minimum of contact resistance and is inherently released by theresilience of a contact carrying arm,y in response tomovement of thearmature. A

In the accompanying drawings in which is shown one of various possibleembodiments of the several features of the invention,

Fig. 1 is a front elevation of the relay.y Fig. 2 is a sectional viewtaken on line 2 2 Fig Pig. 3 is aplan view thereof.-

riaeisadropvedversvecuve otthporuom s Referring now to the drawings, theyoke is desirably made up of a stack Il of E-shaped plates of suitableferrous metal. each lamination including a beam Il, lateral legs I2 anda median leg I3. The stack is held together prior to impregnation bymeans of a single rivet I4 midway through the beam.

Coating with the assembly ot E-shaped laminations is a stack l5 ofI-shaped laminations which has lateral keeper plates Il of non-magneticmetal, desirably of brass, between which the stack of I-laminations issandwiched, the said members being held together by a rivet il midwaytherethrough. a

The keeper plates are desirably provided with ears Il at'the lower edgesthereof bent under the I-stack and serving thereby to prevent thelaminations from pivotal or sliding relative displacement about therivet I1. The keeper plates also have short lateral lugs I9 which in theassembled construction extend'over the extreme laminations of theE-stack at the lateral legs thereof. `Likewise the keeper plates haveunitary therewith longer arms 2li protruding upward from midway betweenthel ends thereof to have sandwiched therebetween they stack oflaminatedmortions makingj up the median leg upon, the E-stack may bereadily assembled with respect to the coil and the I stack by passingthe median leg Il of the E-stack between the two .opstanding arms 2l ofthe keeper pieces, therebypressingthearmsllilrmlyagainstthecoil linerll.Thus the magnetic partsarekept out of contact with coil 2i by theinterposed brass perspective -view ofthe ummm l sectional view on lineties of the keeper arms 25 may now be turned inward as at 23 thereby tomaintain the two stacks of laminations securely assembled. Desirably theends of the keeper arms 20 are bii'urcated as at 24near the top forfacility of assembly, without interference from the heads of the rivetI4 which isexposed between the'arms oi! the bifurcations.

While the air gap of the magnet may be made in conventional manner, itis preferred for this purpose to follow the teachings of the priorapplication of John P. Glass, Serial No. 346,678, filed July 22, 1940.It/may he briefly set forth that for this purpose, there is interposedbetween the contiguous faces of the lateral legs I2 of the E-stackandthe endsof the I-stack, a metal rod or wire 25 that xedly determinesthe size of the air gap and the ends of which may be hooked around thelateral lugs I9 on the keeper plates I6, or if desired, they may bethreaded through corresponding apertures (not shown) inv said keeperlugs. y

The assembly is vacuum impregnated with suitable synthetic resin varnishwhich is later'baked to form a hard insulating coating on the outsidetacts is at the end of a corresponding arm, 43 and 44 respectively, thewidth of which rises from the plate 42 and the length of. which extendslongitudinally of the plate, each of said arms having an outturned baselug 45 riveted as at 48 to the fiber plate. The arm 43 is desirably ofsubstantial length, nearly that of the i'lber plate and of phosphorbronze, spring-hard lto have sufficeint resiliency to -bias the contactcarried thereby away from the companion contact 3l to open circuitposition.

The reduced extremity of the armature 29 at the hinge end thereofdesirably carries a rod 41 of hard ber extending from opposite faces ofsaaid amature. To mount said fiber rod the end of the arma-ture ispreferablybifurcated as at 4B to form lingers 49 which may be spread'apart for insertion of the ,fiber ro'd therebetween and upon forcingthe armsI back jto original pol contact arm 43./ The spring 52 which maybe pregnation, installation or use, for the' keeper plates I6 preventjat all. times any rotary `displacement of anyof the laminations .aboutthe rivets or any lateral spreading of the laminav tions otherwiselikely to occur particularly at tacts 3U and 3l are desirably built asaisub-assembly to be affixed to the main yoke assembly.

This sub-assembly in a preferred embodiment comprises an armature holderplate 32 of nonmagnetic sheet metal, desirably of brass, which has a.transverse stepped slot therein. The widest portion 33 of the slotaccommodates theV entier width of the armature 29 for convenience ofassembly. A contiguous slightly narrower porlateral hinging notches 35in they armature plate. Thenarrowest` portion 35 of the slot definesshoulders 31 to be engaged by one face of the armature plate at theregion lbetween the hinging notches 35, the opposite face of thearmature tion 34 of the slot is of width to be straddled byl plate beingengaged by the outer edge of the`pole 21, when the holder plate isaiilxed in place upon the pole 21 in mannery to be set forth below.

Desirably, the armature holder plate 32 is in' the `form of a bracket'which includes a unitary wing 38 extending generally lengthwise of thearmature, with a tongue 39 at its extremity, which mounts an insulatingfiber button 48 that serves as a limiting stop for the armature in itshinging movement on notches 35.

Riveted as at 4i to the armature holderplate is a liber 'plate-42,uponwhich are mounted the relay contacts 30and 3l. Each ofthese con- -ofSwedish springsteel of .006 inch to .008 inch gauge exerts sufiicientthrust through the' rod 41 to overcome the resilience of contact spring43 and when no current is vpasslngthrough the relay to maintain thecontacts in closed position. By varying the angle of Iwing, 38, thepressure of spring 52fmay be adjusted inI accordance -with requirements.

The sub-assemblyof armature and contacts is Y.

ailixed upon the mainnassembly lby, a pair of machine screws 53 theheads of which are lodged I in corresponding apertures 54 in the berplate, the Shanks of which extend through correspondling small apertures55 in the armature holder plate 32 and the-.points of which are threadedinto corresponding apertures 55 in the pole 21. Slight enlargement ofthe screwapertures 54 and 55 permits minor lateral adjustment in theposiition ofthe sub-assembly, prior totightening the screws into thepole 21 to assure .correctness in the alignment 0f' the armature 29 withrespect to the poles 21 and 28.

When the sub-assembly of armature and con-- tacts is -thus installedupon the main yoke assembly, the end of pole 21 contacts the underface-of the armature 29 and prevents displacement of the hinged part ofthe latter toward the otherwise open larger part 33 of the slot in thearmature holder plate 32. a

The hinge mount-of the armature is thus espel`cially simple andeiiicient, in that it dispenses with pmtle pins and it aiiords Aanon-magnetic hinge for the armature. Y

In operation, 'the free end of the armature 29 strikes the end of pole28. To assure dependable operation, that pole is desirably made ofdouble thickness ofhmagnetic material for concentration of magnetic iluxthereat to enhance its effectiveness. `For this purpose, an. extra'layer 51 of magnetiostock may be spot welded to the leg or To preventoperationof the armature with the frequency of the alternating current,a split phase operation is provided by resort to a shading coll. Thiscoil comprises a fiat1oop'59 of copper passed over a median tongue 30formed by slitting said pole 28 as at 8l to accommodate the lateralwalls i aansn- 3 oftneshsamgeon. miatmumminmnd* 'rne entiremuymybemmuedma byindenting the same into thepole as'at l2. socketorother casing which constitutes no part Thusthe shadingcoildoeanotprotrude to any considerable extentfrom the -pole of the auxiliary yoke,andthe length of the yoke need not be much greater than the height ofcoil 2l, so that the reluctance of the'magnetic circuit through yoke 2land armature 2l is kept low. Desirably, the tongue protrudes slightlybeyond the shading coil as at il, and the lateral portions of the pole2l terminate somewhat below the central portion to avoid engagement bythe armature and to give the proper flux ratios of the split phases,thereby to provide a limited area of impact for the armature and toprevent undesirable vibrations of the armature.

For further assurance of retraction of the armature upon collapse oi'the magnetic field, means is provided to overcome the residual magneticattraction of the pole faces for the armature when of the presentinvention, and is, therefore, not

lWhen no current traverses the apparatus, the spring I2 by pressuretransmitted through button 41 maintains the amature 2| against stop 40and` over-powers the resilient contact carrying arm 4I to retain it inclosed circuit position. In the use in thermionic lighting circuits forinstance, when the circuit is closed, the armature the coil isde-energized. To this end a non-mag- -or on the armature, but preferablyon the latter.

To this end, the plated region of the amature that strikes the pole mustpresent a thickness of non-magnetic character and a strikin surface areaof sufficient hardness to withstand the repeated impacts withoutappreciable wear or deformation. This coating may be plated upon thearmature according to any approved practice, desirably byelectroplating. A desirable striking contact metal is hard chromium, butsince that metal has magnetic properties, it would, if plated directlyupon the ferrous metal of the amature lack complete effectiveness forquick release. Therefore, hard chromium is used as the facing layer 64and is plated upon a base plated layer Si of non-magnetic metal,desirably of copper, which latter is too soft to withstand the impact.Desirably thehun-magnetic layer 65 20 is attracted to pole 2l by pivotalmovement and the rod 41 engaging spring I2V moves toward said spring anddisplaces it and moves away from the spring arm 4l, which by virtue oi'its inherent bias moves the contact ll to open circuit position, whichopen position is maintained as long as sumcient current is passingthrough the coil 2 l a condition maintained during the normal operationof the lamp. In the starting operation, the stop 4l not only limits themaximum open- A ing movement of the armature, and therefore of'copper bywhich vthe magnetic iiux dissipation at the striking area is promoted,has a thickness in the order of .0025 inch, while the hard chromiumfacing 64 may have a thickness in the order of .0005 inch.

For ease and neatness of installation it is desirable to extend downwardand outward from the middle portion of the keeper plates i6. a pair ofsupporting or carrying legs 66 for the'unit. 'I'hese legs may be bentout as unitary parts of said keepers extending between the ears ildownward and outward, desirably at an angle'of about degrees, withhorizontal'diverging toes or feet 61 bifurcated as at 6I. These feet maystraddle annular grooves 69 in small rubber grommets 10 through whichheadedA fastening screws 1I extend for mounting the unit inposition, awasher 1l transmitting the thrust from the screw head to the grommet.The mounting means set forth affords a secure foundation for the relay,which will transmit no mechanical noises of operation or residuallamination hum to the socket or other device to which the relay isattached.

The legs 6B also aorda convenient location for the small condenser 12disposed .under the magnetic yoke and desirably held in place againstsaid yoke by a phosphor bronze band l2 threaded at its endsthroughcorresponding slotsV 14 in the maximum'air gap between kthearmature and the poles of yoke 2t, but it also cushions the vibratoryaction of the armature. 'I'he damped operation of armature as set forthresults in improved action, in that blackening of the fluorescent lampson their ends occurs only after a much larger number of starts than ifan undarnped armature mount were provided.

As soon as the magnetic iiux through the yoke lll-l5 collapses eitherdue to disturbance in operation or opening of the circuit. the spring 52by pressure upon rod y41 moves the armature away from the pole 2l andthe thrust transmitted through said rod 41 urges the arm 4l to contactclosing position.v The prompt release action results from the fact thatthe non-magnetic copper plated layerllupon the armature avoidsthemagnetic retentivity which otherwise would delay release of thearmature and reclosure of the relay contacts. The reduced area ofcontact between yoke and-armature by reason of the foreshortening ofthe'lateral parts of the pole 28 also contributes to the prompt releaseof the armature. y

The shading coil il is particularly eiective by its split phase actionto maintain the armature in contact with the pole during the reversalsof flux in the normal alternating current operation, so that hum orchattering of the armature is avoided. y

'I'hus the parte making up the relay are readily assembled as twosub-assembliesfthe main yoke assembly and the armature and-contactassembly, and the latter is readily mounted upon the former as setforth. The spring arm 42 need doy no mechanical work other than to carryits contact 30 to open circuit position when rod 41 recedes therefrom.The retraction of the armature from the yoke is effected by the pressureof spring 52 independently of the spring arm 43. Thus contact closure isreliably maintained with a low resistance contact, and this would not bedisturbed even if in'operation the fiber plate 42 were to warp underdistortion due to heat o other strain.

The intervening brass arm 20 magnetically sep- `arating the main yokeIII- Il from the auxiliary sired larger voltage across coil 2i foreffective attraction of the armature.

I'he electro-magnet and yokestxucture as such f is the smeet ofdivisional application sleriorno.

527,409 :liled March 2l, 1944. i

As many changes could lbe made in the above apparatus and manyapparently widely dinerent embodiments of this invention could be madewithout departing from the scope of the claims. it is intended that allmatter contained 4in the above description or shown in the accompanying;drawings shall be interpretedas illustrative and not in a limitingsense. o

Having thus described my invention, what I claim as new and desire tosecure by Letters Pat- 'entis: v

1'. In a relay of the type that comprises a magnetic yoke having a fixedair gap, an electromagnetic coil about one arm of said yoke and anauxiliary yoke through said coil having a pair of poles straddling saidcoil and an armature and contact assembly associated with said latteryoke;

the combination in which Asaid assembly comprises a non-magnetic sheetmetal bracket in-V cluding a plate and a Wing. said' plate beingremovably ailixed in face to face engagement with one of said'poles. anamature extending through fa slot in said bracket plate andA havinglateral notches straddling 'the ends of said slot, said armaturebridging across said poles, and the extremity thereof protruding beyondsaidbracket,

an insulating plate ailixed to said bracket plate.- s

Y a pair of' contact arms riveted to said insulating plate, one of saidcontact arms being resilient and biased to open contact position,thawing of said bracket having an armature'stop near its lower end,a'leaf spring riveted to said wing and extending upward therefrom, andan insulating rod carried by `and extending transversely through theprotruding end `of saidarmature and engaging and serving as a thrusttransmitter between said spring' and said resilient. contact arm.

2. In a relay structure of the type that comprises a magnetic yoke, anelectro-magnetic coil y encircling one portion thereof, .an auxiliaryyoke through said coil having a pair of poles straddling the samel andan armature and contact assembly associated with the latter yoke; thecombination in which said assembly comprises a nonmagnetic metal platesuperposed over one ot said l poles, an armature accommodated in\acorrespending slot in said plate and having notches straddling aportionof said slot, said amature bridging across the ends of the twopoles, a :liber plate riveted to said metal plate, a pair of coactingcontact members amxed to said ilber plate, and a pair of aperturesthrough said :ber and metal plates, to coact with correspondingapertures of smaller diameter in the pole adjacent said metal plate andscrews aihxing said metal and ilber plates to said pole, the aperturesthrough the latter plates being somewhat larger than those through thepole to permit minor adjustment for correct registry -of the amaturewith respect to the poles in the tightening of said screws.

s 3. An armature and contact assembly for a relay, said assemblycomprising `a non-magnetic sheet metal hinge plate, an armature havinglateral notches extending through a'corresponding asuma' tending atright angles to said carrier plate, said` arms each having an outturnedbase lug near the end thereof remote from the contact carrying end, saidlugs resting upon and being afiixed to said insulating carrier plate,and transmission means between ysaid armature and one of said contactarms. l 4. An armature and contact'assembly for a relay, said assemblycomprising a non-magnetic angle shaped sheet metal piece. an amatureplate having notches straddling the edges of a corresponding aperture insaid piece for hinge Vmount thereat, an insulating carrier plate aiilxedto one face of said angle shaped piece and extending substantially atright angles to said amature, a contact maker including a resilientcontact carrying arm fixed to said insulating carrier plate, aleafspring riveted to one army of said angle shaped piece and extendingsubstantially at right angles to the insulating car` rier plate. aninsulating rod carried by the free extremity of said armature near thehinge thereofl and resilientlyengaged at the opposite ends thereofrespectively by said leaf spring and said resilient contact carryingarm.

5. An armature and contact assembly for a relay, said assemblycomprisinga bracket of non-magnetic sheet metal including a-plate and awing element, an armature plateextending through a correspondingvgenerally rectangular opening in the plate portion of said bracket andhaving lateral notches straddling the edges of said opening, saidarmature having an extension beyond said hinge and protruding from saidbracket,an insulating rod carried by said armature end, an finsulatingplate carried by' the plate portion'of said bracket, a pair of contactmembers carried by said insulating plate, one of said members'comprisinga resilientl contact carrying arm engaging one end of said insulatingrod and'biased to contact opening position, and a leaf spring riveted tothe wing part of said bracket a'nd resiliently engaging the opposite endof said rod, thawing of saidbracket ,having an armature stop.

In a relayof the type set forth the combination of an electro-magneticcoil, a U-shaped yoke therethrough having poles straddling said eralnotches of said armature, said plate having i plate.

a still narrower slot portion affording stop shoulders for the width ofthe armature between lsaid notches, the end of said'pole engaging theYrear face of said armature adjacent said holding ADoLPn wansnna. I

